bisecting fixing commit since a844dc4c544291470aa69edbe2434b040794e269
building syzkaller on 0ae38e44894e5a52fe35a56b1d2ad18477cc6b59
testing commit a844dc4c544291470aa69edbe2434b040794e269 with gcc (GCC) 8.1.0
kernel signature: 9e329099256f99d1d0aa07bbee4fcd544b03bd403c9775cb82482f530762749b
all runs: crashed: BUG: unable to handle kernel paging request in insert_char
testing current HEAD 78d697fc93f98054e36a3ab76dca1a88802ba7be
testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0
kernel signature: 3d7735c9edd2d8876770e6d38cc9b614db4f163900b463086e724a807ba26a34
all runs: crashed: BUG: unable to handle kernel paging request in insert_char
revisions tested: 2, total time: 24m31.462671964s (build: 16m59.336121345s, test: 6m25.389028276s)
the crash still happens on HEAD
commit msg: Linux 4.14.172
crash: BUG: unable to handle kernel paging request in insert_char
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
BUG: unable to handle kernel paging request at 000000010000000e
IP: memset16 arch/x86/include/asm/string_64.h:58 [inline]
IP: scr_memsetw include/linux/vt_buffer.h:36 [inline]
IP: insert_char+0xfe/0x280 drivers/tty/vt/vt.c:535
PGD 950f4067 P4D 950f4067 PUD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7077 Comm: syz-executor.2 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880902444c0 task.stack: ffff8880968c8000
RIP: 0010:memset16 arch/x86/include/asm/string_64.h:58 [inline]
RIP: 0010:scr_memsetw include/linux/vt_buffer.h:36 [inline]
RIP: 0010:insert_char+0xfe/0x280 drivers/tty/vt/vt.c:535
RSP: 0018:ffff8880968cf788 EFLAGS: 00010202
RAX: 0000000000000720 RBX: ffff88809f04e5c0 RCX: 0000000000000001
RDX: 1ffff11013e09d31 RSI: 000000010000000e RDI: 000000010000000e
RBP: ffff8880968cf7b8 R08: 0000000000000001 R09: ffff88809f04e5c0
R10: 00000000000000c8 R11: ffff8880902444c0 R12: 0000000000000001
R13: 000000010000000e R14: ffff88809f04e94c R15: ffff88809f04e8f4
FS:  00007f868ca19700(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000010000000e CR3: 0000000099518000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 csi_at drivers/tty/vt/vt.c:1627 [inline]
 do_con_trol+0x1f3c/0x61a0 drivers/tty/vt/vt.c:2074
 do_con_write.part.22+0x9bc/0x19c0 drivers/tty/vt/vt.c:2434
 do_con_write drivers/tty/vt/vt.c:2205 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:2787
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x498/0x1040 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x346/0x770 drivers/tty/tty_io.c:1043
 __vfs_write+0xdb/0x840 fs/read_write.c:480
 vfs_write+0x150/0x4f0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0x100/0x250 fs/read_write.c:582
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a909
RSP: 002b:00007f868ca18c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a909
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f868ca196d4
R13: 00000000004cbdc5 R14: 00000000004e5a58 R15: 00000000ffffffff
Code: df 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 01 0f 8e 35 01 00 00 44 89 e1 0f b7 83 c8 03 00 00 4c 89 ef 81 e1 ff ff ff 7f <f3> 66 ab 48 8d bb 78 04 00 00 48 b8 00 00 00 00 00 fc ff df 48 
RIP: memset16 arch/x86/include/asm/string_64.h:58 [inline] RSP: ffff8880968cf788
RIP: scr_memsetw include/linux/vt_buffer.h:36 [inline] RSP: ffff8880968cf788
RIP: insert_char+0xfe/0x280 drivers/tty/vt/vt.c:535 RSP: ffff8880968cf788
CR2: 000000010000000e
---[ end trace 9e40e0563c89c653 ]---